FWIW and IMHO, it's not really a bonus track if the artist wrote and/or arranged the tune, recorded it and intended to release it along with the rest of the tunes on the album. Just a ploy by the marketing-heads at the labels to make the consumer think they are getting a "bonus". If a tune that's on a CD can't be played on my computer, I'm pissed off.
Off topic - When cassettes became popular, they would include bonus tracks, compared to the vinyl version. Later, you would get a bonus track(s) on a CD, as opposed to a cassette, when Sony and Philips were trying to get consumer acceptance for that new format. In turn, bonus enhanced material was included on CD's. When the maximum time that could be stored to a CD was discovered, some artists simply recorded as much as they could write. Some ECM recordings extend to 80+ minutes.
Off topic - When cassettes became popular, they would include bonus tracks, compared to the vinyl version. Later, you would get a bonus track(s) on a CD, as opposed to a cassette, when Sony and Philips were trying to get consumer acceptance for that new format. In turn, bonus enhanced material was included on CD's. When the maximum time that could be stored to a CD was discovered, some artists simply recorded as much as they could write. Some ECM recordings extend to 80+ minutes.